1. Field of the Invention
The present invention relates to a transmission control system for and method of an automotive vehicle employing a continuously variable automatic transmission, and specifically to techniques for optimally controlling a speed ratio, which states the ratio of the transmission input to output speed, of an automobile continuously variable automatic transmission even under particular vehicle driving conditions, for example when restarting after the vehicle experiences wheel spin at drive road wheels during the starting period on uphill roads with wheel spin, or when restarting after the vehicle experiences wheel spin at drive wheels during the starting period on low-.mu. roads.
2. Description of the Prior Art
Japanese Patent Provisional Publication Nos. 8-178042 and 4-54371 have disclosed a belt-type continuously variable automatic transmission, often abbreviated to "CVT". Generally, the speed ratio of the CVT is electronically controlled in accordance with a predetermined speed-change pattern by means of an electronic transmission control unit. The predetermined speed-change pattern is pre-stored as a preprogrammed characteristic map in the memory (ROM) of the transmission control unit. A desired speed necessary for the speed-change control action is generally based on vehicle speed and engine load. As a control parameter corresponding to the vehicle speed, a rotational speed of the output shaft of the CVT (i.e., a drive-wheel speed) is generally used.